Ethfinex is a cryptocurrency exchange focused on ERC20 compatible tokens that was created by Bitfinex. It aims to be, not only a trading platform, but also a community discussion platform for ERC20 compatible tokens and ethereum-based ICOs.

Ethfinex is a hybrid decentralized exchange. Traders can choose between trustless on-chain settlement, or high speed centralized execution. By using decentralized remote portals, users can access the Ethfinex order book without actually having to deposit their funds with Ethfinex. Ethfinex also has a robust API, remote portals, and margin trading.

Ethfinex wants to be a hub for the overall ERC20 token community. It is a good option for those looking to trade tokens, but it also a platform that can be used by Ethereum developers for their crowd-sourcing needs.

Ethfinex has a user-friendly interface but it is primarily designed for intermediate and advanced traders. It offers margin trading, a crowdfunding funding market, and an active discussion forum about ERC-20 projects. It has a wide range of order types available, including the basic market, limit and stop loss orders.

Ethfinex has a variety of security features, such as cold wallets that require multiple managers to unlock. There are also a number of automatic verification tools in place, and 2-factor authentication is encouraged for all accounts.
Ethfinex features its own token, the Nectar tokens (NEC). NEC tokens are given for free to token market makers in proportion to the volume of trades they participate in on the exchange.

Trading Fees: Tiered system depending on volume ranging from 0.1%-025%

Bittrex is one of the largest crypto to crypto exchanges. It offers a large number of trading pairs, but do not allow fiat to crypto trading. Bittrex has one of the largest trading volumes in the market.
It is a reputable exchange with good record on security and is also fully regulated. They provide two factor authentication as well as a number of other options to secure funds. They are United States based and are fully compliant with all laws.
They support more than 190 cryptocurrencies and have a dynamic platform. It’s a good option for both advanced and beginner traders; providing advanced tools like candlestick charts and crosshairs, but with a user-friendly interface that is very intuitive.
Trading Fees: 0.25%

BitFinex is a bitcoin to fiat exchange, a margin trading exchange, and a liquidity provider. The platform offers a number of features that expand the financial positions you can take - for example the ability to short Bitcoin via margin trading.
The exchange also offers a set of other cryptos apart from bitcoin such as Litecoin and Ethereum.
Deposits and withdrawals take place via the standard bank transfer means with fees of 0.1% and a minimum of $20. Bitcoin and Litecoin are free.
BitFinex takes security seriously and have moved from a hot wallet cold wallet set up to segregating customer funds where each user has access to their own wallet which they can review on the blockchain.
Bitfinex was hacked on 03 August 2016 and around 120,000 BTC were stolen.
Fee of 0.1% for most trades